Large scale preparation of 20 cm × 20 cm graphene modified carbon felt for high performance vanadium redox flow battery

Vanadium redox flow batteries (VRFBs) are widely applied in energy storage systems (e.g., wind energy, solar energy), while the poor activity of commonly used carbon-based electrode limits their large-scale application. In this study, the graphene modified carbon felt (G/CF) with a large area of 20 cm ׁ 20 cm has been successfully prepared by a chemical vapor deposition (CVD) strategy, achieving outstanding electrocatalytic redox reversibility of the VRFBs. The decorating graphene can provide abundant active sites for the vanadium redox reactions. Compared with the pristine carbon felt (CF) electrode, the G/CF composite electrode possesses more defective sites on surface, which enhances activity toward VO²⁺/VO₂⁺ couple and electrochemical performances. For instance, such G/CF electrode delivered remarkable voltage efficiency (VE) of 88.4% and energy efficiency (EE) of 86.4% at 100 mAdcm^-2, much higher than CF electrode by 2.1% and 3.78%, respectively. The long-term cycling stability of G/CF electrode was further investigated and a high retention value of 47.6% can be achieved over 600 cycles. It is demonstrated that this work develops a promising and effective strategy to synthesize the large size of carbon electrode with high performances for the next-generation VRFBs.